Knee prosthesis

ABSTRACT

A knee joint prosthesis assembly can include a femoral component that has a medial and a lateral condyle portion connected by a patellar track portion. The femoral component can form an opening between the medial and lateral condyles. A tibial component can have a medial portion that includes a first engagement structure and a lateral portion that includes a second engagement structure. A medial bearing can have a third engagement structure formed thereon that selectively engages the first engagement structure. A lateral bearing separately formed and independent from the medial bearing can have a fourth engagement structure formed thereon that selectively engages the second engagement structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 12/788,961 filed on May 27, 2010 which claims the benefit and priority of 61/181,938, filed May 28, 2009. The entire disclosure of the above applications is incorporated herein by reference.

FIELD

The present disclosure relates to a knee joint prosthesis including a tibial tray component having independent and selectively attachable bearings including fixed and mobile bearings that can be secured to medial and lateral sides of the tibial tray according to the needs of a particular patient.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

A knee joint prosthesis can generally comprise a femoral component and a tibial component. The femoral component and the tibial component can be designed to be surgically attached to the distal end of the femur and the proximal end of the tibia, respectively. The femoral component can further be designed to cooperate with the tibial component in simulating the articulating motion of an anatomical knee joint. In many examples, the tibial component can further include a bearing component that includes articulation surfaces on the medial and lateral side for cooperating with a medial and lateral condyle portion of the femoral component. In some examples, the bearing component can be fixed relative to the tibial component. In other examples, the bearing component can be a mobile bearing component that has at least a portion that can move relative to the tibial component during articulation of the femoral component.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

A knee joint prosthesis assembly can include a femoral component that has a medial and a lateral condyle portion connected by a patellar track portion. The femoral component can form an opening between the medial and lateral condyles. A tibial component can have a medial portion that includes a first engagement structure and a lateral portion that includes a second engagement structure. A medial bearing can have a third engagement structure formed thereon that selectively engages the first engagement structure. A lateral bearing separately formed and independent from the medial bearing can have a fourth engagement structure formed thereon that selectively engages the second engagement structure.

According to other features, one of the medial and lateral bearings can be fixed relative to the tibial component and the other of the medial and lateral bearings can be a mobile bearing component.

According to still other features, the mobile bearing component can include a fixed portion that has the third or fourth engagement structure that is configured to statically engage the tibial component and a mobile bearing portion that is configured to slidably advance along the opposing surface of the tibial component. The fixed portion can define a pocket that receives and confines the mobile bearing portion therewithin. The mobile bearing portion can be formed of a polymeric material and can include a metallic layer of material disposed around a perimeter thereof.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is an anterior perspective view of a knee prosthesis assembly according to one example of the present teachings;

FIG. 2 is a posterior perspective view of the knee prosthesis of FIG. 1;

FIG. 3 is a lateral perspective view of a femoral component of the knee prosthesis of FIG. 1;

FIG. 4 is a superior perspective view of a tibial tray of the knee prosthesis of FIG. 1;

FIG. 5 is an inferior perspective view of the tibial tray of FIG. 4;

FIG. 6 is a perspective view of a mobile bearing of the knee prosthesis of FIG. 1;

FIG. 7 is a perspective view of a fixed bearing of the knee prosthesis of FIG. 1;

FIG. 8 is a perspective view of a locking bar associated with the fixed bearing of a knee prosthesis of FIG. 1;

FIG. 9 is a partially exploded posterior view of a knee prosthesis constructed in accordance to additional features of the present teachings;

FIG. 10 is a posterior perspective view of the knee prosthesis of FIG. 9;

FIG. 11 is an anterior perspective view of a tibial tray and fixed bearing portion of the knee prosthesis of FIG. 10;

FIG. 12 is a perspective view of a mobile bearing that slidably cooperates within a pocket formed on the fixed bearing of FIG. 11;

FIG. 13 is an anterior perspective view of a knee prosthesis assembly according to another example of the present teachings that incorporates a mobile bearing component that is selectively attachable to a medial side of a tibial tray and a fixed bearing component that is selectively attachable to a lateral side of the tibial tray;

FIG. 14 is an anterior superior exploded perspective view of the knee prosthesis assembly of FIG. 13;

FIG. 15 is an anterior inferior exploded perspective view of the knee prosthesis assembly of FIG. 13;

FIG. 16 is a perspective view of a mobile bearing incorporating a metal sleeve according to various features;

FIG. 17 is an anterior perspective view of a tibial tray constructed in accordance to additional features and incorporating a pair of fixed bearings that are selectively locked to the tibial tray with a locking bar;

FIG. 18 is an anterior superior exploded perspective view of the tibial tray assembly of FIG. 17;

FIG. 19 is an anterior inferior exploded perspective view of the tibial tray assembly of FIG. 17;

FIG. 20 is an anterior perspective view of a tibial tray constructed in accordance to additional features of the present teachings; and

FIG. 21 is a kit having a plurality of tibial trays, medial bearings and lateral bearings according to the present teachings.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.

With initial reference to FIGS. 1 and 2, a knee prosthesis assembly constructed in accordance to one example of the present teachings is shown and generally identified at reference numeral 10. The knee prosthesis assembly 10 can generally include a femoral component 12, a tibial tray 14, a medial floating or mobile bearing 16 and a lateral fixed bearing 18. As will be described, the knee prosthesis assembly 10 can be used when it is desirable to retain or reconstruct an anterior cruciate ligament (ACL) and/or a posterior cruciate ligament (PCL).

The respective components of the knee prosthesis assembly 10 can be patient specific, such that each component can be constructed for optimal features for a given patient. For example, the bone interface margins of the femoral component 12 and tibial tray 14 can be patient specific for optimized bone coverage. In addition, the overall size, such as anterior-posterior dimensions and bone cut geometry can be determined and used for manufacturing the components of the knee prosthesis assembly 10. Moreover, some articulation features can be determined and used as criteria for forming the components of the knee prosthesis assembly 10. In sum, each of the components of the knee prosthesis assembly 10 can be a patient-specific implant, a semi-custom implant or an off-the-shelf or standard production implant. A custom-made implant is a patient-specific, one-of-a-kind implant specifically made for a particular patient, and consequently there is no inventory associated with such implant. Standard or off-the shelf implants are available and stocked in a number of sizes, typically six or more, and a number of configurations or types, including bilateral or unilateral implants, constrained, semi-constrained, mobile, etc. Because of the variety of sizes and configurations that are kept in stock to be accommodated by different patients, a large inventory of standard implants is created, and several molds for each type and size of implant may be used. Semi-custom implants can provide an intermediate solution between custom-made and off-the-shelf implants. Semi-custom implants reduce the size of inventory and molds required for production, while allowing some degree of patient-specific customization. Additional description of patient-specific implants and semi-custom implants and their implementations may be found in copending patent application Ser. No. 12/103,824, filed Apr. 16, 2008 and entitled: Method and Apparatus for Manufacturing an Implant, the disclosure of which is hereby incorporated by reference.

With additional reference to FIG. 3, the femoral component 12 will now be described in greater detail. The femoral component 12 can generally comprise a cruciate retaining prosthesis and includes various portions to replace or mimic the distal femur. The femoral component 12 can include a medial condyle portion 20 and a lateral condyle portion 22. The condyle portions 20 and 22 can replace the medial and lateral condyles of a distal femur. The medial and lateral condyle portions 20 and 22 can interconnect and be formed as a single piece with a patellar track portion 26. The patellar track portion 26 can allow for articulation of a patella, either natural or prosthetic patella, once the femoral component 12 is implanted onto the distal femur. The medial and lateral condyle portions 20 and 22 and the patellar track portion 26 can generally define an exterior portion of the femoral component 12. The femoral component 12 can define an opening or passage 30 between the medial and lateral condyle portions 20 and 22. As can be appreciated, the passage 30 can accommodate, and provide clearance for a host ACL and/or PCL or a reconstructed ACL and/or PCL. The medial condyle portion 20 can include a spherical contact surface that is convex in an anterior/posterior direction and a medial/lateral direction.

The femoral component 12 can include a bone contacting or inferior surface 34 (FIG. 2). The inferior surface 34 can include an anterior surface 36 that can be substantially flat and formed generally parallel to a pair of posterior surfaces 38 a and 38 b. A pair of intermediate surfaces 40 a and 40 b are provided generally at an intermediate portion of the inferior surface 34. A pair of angled anterior transition surfaces 42 a and 42 b generally connect the anterior surface 36 with the intermediate surfaces 40 a and 40 b. Similarly, a pair of angled posterior transition surfaces 44 a and 44 b are provided between the respective posterior surfaces 38 a and 38 b and the intermediate surfaces 40 a and 40 b. In one example, a threaded boss 50 a and 50 b can be provided on each of the intermediate surfaces 40 a and 40 b, respectively. Similarly, a threaded boss 52 a and 52 b can be provided on the posterior surfaces 38 a and 38 b, respectively. The bosses 50 a, 50 b, 52 a and 52 b can be optionally used to threadably couple with various augments (not specifically shown) as necessary. The femoral component 12 can be formed as a unitary structure and cast of a biocompatible high strength alloy, such as cobalt-chromium-molybdenum alloy or similar suitable material. All surfaces, which do not contact the femur, can be highly polished to provide smooth articulating bearing surfaces. The interior surface 34 of the femoral component 12 can be roughened or uneven or include porous material to allow bone ingrowth or attachment with bone cement. Other features of the femoral component 10 can include those associated with the Oxford® Partial Knee marketed by Biomet, Inc.

With reference now to FIGS. 1, 2, 4 and 5, the tibial tray 14 will now be described in greater detail. The tibial tray 14 can include a generally U-shaped body having a medial portion 60 and a lateral portion 62. A slot 64 can be formed in the tibial tray 14 generally between the medial and lateral portion 60 and 62. As with the passage 30 of the femoral component, the slot 64 of the tibial tray 14 can accommodate and provide a clearance for a host ACL and/or PCL or a reconstructed ACL and/or PCL. During implantation, the tibial tray 14 can be advanced posteriorly, such that the slot 64 can accommodate a host ACL and/or PCL. In instances where a reconstructed ACL and/or PCL is used, a tray (and bearing) having a passage can be utilized. One suitable configuration is further described in commonly owned in U.S. Pat. No. 7,255,715; issued Aug. 14, 2007 and is hereby incorporated by reference. The tibial tray 14 can include an inferior bone engaging side 66 (FIG. 5) and a superior bearing engaging side 68 (FIG. 4). The medial portion 60 of the superior bearing engaging side 68 can include a highly polished tibial bearing surface 70. A rail 72 can extend in a generally anterior/posterior direction adjacent to the highly polished tibial bearing surface 70. The lateral portion 62 can include engaging structure 78 provided on the superior bearing engaging side 68. The engaging structure 78 can include a pair of posts 80 and 82 integrally formed at an anterior edge thereof. A retaining rail 84 can extend superiorly from a posterior edge of the lateral portion 62. The posts 80 and 82 can both have an anterior groove 86 and a posterior groove 88, respectively. The retaining rail 84 can have a transverse groove 90 formed on an inwardly facing surface. The tibial tray 14 can be generally manufactured of cobalt-chromium-molybdenum alloy or other suitable biocompatible material. A pair of fins 94 can extend from the inferior bone engaging side 66. While fins 94 are shown operatively associated with the tibial tray 14, other structures suitable for engaging a proximal tibia can include pegs, posts or porous material can additionally or alternatively be provided on the inferior bone engaging side 66.

With reference to FIGS. 1, 2 and 6, the medial floating bearing 16 will now be described in greater detail. The medial floating bearing 16 has a substantially planar inferior bearing surface 100 which slidably moves and articulates relative to the highly polished tibial bearing surface 70. The medial floating bearing 16 further includes a first bearing surface 102. The first bearing surface 102 articulates with the medial condyle portion 20 of the femoral component 12. The medial floating bearing 16 can be formed from a surgical grade, low friction, and low wearing plastic, such as ultra high molecular weight polyethylene (UHMWPE) or other suitable material.

With reference to FIGS. 1, 2 and 7, the lateral fixed bearing 18 can include engaging structure 106 formed on an inferior surface for coupling with the engaging structure 78 provided on the lateral portion 62 of the tibial tray 14. The engaging structure 106 can generally include a posteriorly extending lip 110 and an anterior groove 112. A locking bar 114 (FIG. 8) can be slidably inserted through the anterior groove 112 to interlock between the respective grooves 86 to capture the lateral fixed bearing 18 to the lateral portion 62 of the tibial tray 14. The posteriorly extending lip 110 can be nestingly received by the retaining rail 84. The lateral fixed bearing 18 can include a second bearing surface 120. The second bearing surface 120 can articulate with the lateral condyle portion 22 of the femoral component 12. The lateral fixed bearing 18 can be formed from a surgical grade, low friction and low wearing plastic, such as UHMWPE or other suitable material.

During use, the medial and lateral condyle portions 20 and 22 of the femoral component 12 can articulate on the first and second bearing surfaces 102 and 120 of the respective medial floating bearing 16 and lateral fixed bearing 18. As can be appreciated, the lateral fixed bearing 18 is static relative to the tibial tray 14 during articulation of the femoral component 12. The medial floating bearing 16 is free to slide along the highly polished tibial bearing surface 70 of the medial portion 60 of the tibial tray 14. The medial floating bearing 16 is bound on an inboard side by the rail 72.

While the embodiment shown in the figures includes a floating bearing provided on a medial side and a fixed bearing provided on a lateral side, the location of these bearings can be swapped. Similarly, both of the medial and lateral sides can be formed with floating bearings or fixed bearings. Turning now to FIGS. 9-11, a knee prosthesis assembly constructed in accordance to additional features of the present teachings is shown and generally identified at reference numeral 210. The knee prosthesis assembly 210 can generally include a femoral component 212, a tibial tray 214, a medial side having a mobile bearing component 216 and a lateral side having a fixed bearing 220. The mobile bearing component has a fixed portion 217 and a mobile bearing portion 218. The femoral component 212 can be constructed similar to the femoral component 12 described below. The fixed bearing 220 can be constructed similar to the lateral fixed bearing 18 described above. The mobile bearing component 216 can provide articulation that is fully conforming with the femoral component 212. The mobile bearing portion 218 can be captured around its perimeter by a pocket 222 formed by the fixed portion 217. In this way, the mobile bearing portion 218 can have a reduced likelihood of becoming dislocated relative to the fixed portion 217. While the mobile bearing component 216 is shown generally associated with the lateral side of the tibial tray 214, such a configuration can be additionally or alternatively provided on the medial portion of the tibial tray 214. In one example, the mobile bearing portion 218 can be formed by polyethylene or polyetheretherketone (PEEK). As shown in FIG. 11, the fixed portion 217 can have a pair of channels 226 formed thereon for guiding tabs 230 provided on the mobile bearing portion 218 (FIG. 12). It will be appreciated that while the mobile bearing component 216 has been described and shown incorporated on a medial portion of the tibial tray 214, it can additionally or alternatively be incorporated on a lateral portion of the tibial tray 214. Likewise, while the fixed bearing 220 has been described and shown incorporated on a lateral portion of the tibial tray 214, it can additionally or alternatively be incorporated on a medial portion of the tibial tray 214.

With reference now to FIGS. 13-16, a knee prosthesis assembly 310 constructed in accordance to additional features of the present teachings will be described. As with the other knee prosthesis assemblies disclosed herein, the knee prosthesis assembly 310 can be patient specific, such that each component can be constructed for optimal features for a given patient. In this regard, the knee prosthesis assembly 310 can generally include the femoral component 12, a tibial tray 314, a mobile bearing component 316 and a fixed bearing component 318. As shown, the mobile bearing component 316 is selectively secured to a medial portion 320 of the tibial tray 314 and a fixed bearing component 318 selectively secured to a lateral portion 322 of the tibial tray 314 for a left knee. However, it will be appreciated by those skilled in the art that a mobile bearing component 316 can be provided for both the medial portion 320 and the lateral portion 322 of the tibial tray 314. Similarly, a fixed bearing component 318 can be provided for both of the medial portion 320 and the lateral portion 322 of the tibial tray 314. Likewise, the fixed bearing component 318 can alternatively be provided only on the medial portion 320, while a medial bearing component 316 can be provided only on a lateral portion 322 of the tibial tray 314. In sum, any combination of mobile and fixed bearing components can be available and selectively secured to either of the medial or lateral portions 320 and 322 of the tibial tray 314.

The femoral component 12 can be generally formed similar to the femoral component 12 described in detail above. Again, the medial condyle portion 20 can have a spherical, convex articulation surface that can cooperate with the mobile bearing components 316 as will be described herein. It is appreciated that a similar spherical, convex articulation surface can be provided on the lateral condyle portion 22 in the event that a mobile bearing component is desired on the lateral portion 322 of the tibial tray 314.

The mobile bearing component 316 can generally include a fixed portion 330 and a mobile bearing portion 332 (FIG. 14). The fixed portion 330 can generally include a pocket 334 defined within a surrounding wall 336. A superior surface 338 can be contoured to cooperate with the profile of the medial condyle portion 20 of the femoral component 12. An inferior surface 340 (FIG. 15) can have a channel 342 that tapers generally anteriorly for locking with a portion of the tibial tray 314 as further discussed herein. The pocket 334 extends through the fixed portion 330 from the superior surface 338 to the inferior surface 340 to permit an inferior surface 354 of the mobile bearing portion 332 to abut the tibial tray 314. A rail 346 can be formed into the surrounding wall 336. A groove 348 can be formed around a posterior edge of the fixed portion 330. The fixed portion 330 can have an inner wall 349 that cooperates with the U-shaped profile of the tibial tray 314 to accommodate a host or reconstructed ACL.

The mobile bearing portion 332 can have an outer perimeter surface 350 that substantially matches a profile of the surrounding wall 336, however, is reduced in size so as to be stepped inwardly relative to the surrounding wall 336 (see also FIG. 9) to allow movement within the surrounding wall 336. Tabs 352 can extend in generally the medial and lateral directions from the inferior surface 354 of the mobile bearing portion 332. A superior articulating surface 358 can substantially conform to the profile of the medial condyle portion 20 of the femoral component 12. The fixed portion 330 and the mobile bearing portion 332 can be formed of UHMWPE or PEEK. According to additional features, a mobile bearing portion 332′ (FIG. 16) can have a metal layer or band 359 disposed around a perimeter. The metal layer 359 can preclude polymer-polymer contact between the perimeter of the mobile bearing portion 332′ and the surrounding wall 336 of the fixed portion 330 to inhibit wear. As shown in FIG. 16, similar features are identified with common reference numerals having a “prime” suffix.

The fixed bearing component 318 can generally include a superior surface 360 that substantially conforms to and provides a surface contact with the profile of the lateral condyle portion 22 of the femoral component 12. A channel 362 can be formed along an anterior inferior surface 364 and that generally tapers anteriorly. A groove 368 can be formed around a posterior edge of the fixed bearing component 318. The fixed bearing component 318 can have an inner wall 369 that cooperates with the U-shaped profile of the tibial tray 314 to accommodate a host or reconstructed ACL.

The tibial tray 314 can generally include a locating tab 370 formed on an anterior edge of the medial portion 320 and a locating tab 372 formed on an anterior edge of the lateral portion 322. A slot 374 can be defined through the tibial tray 314 between the medial and lateral portions 320 and 322. The slot 374 can be configured to accommodate and provide clearance for a host ACL and/or PCL or a reconstructed ACL and/or PCL. A retaining rail 375 can be formed around a posterior edge of the medial portion 320. The retaining rail 375 can include a lip 376 and a groove 378. A retaining rail 380 can be formed around a posterior edge of the lateral portion 322 of the tibial tray 314. The retaining rail 380 can generally include a lip 382 and a groove 384. An inferior surface 386 of the tibial tray 314 can be generally smooth, but may also incorporate a series of round grooved pegs. The inferior surface 386 can be configured to be cemented or press-fit onto the proximal tibia. The tibial tray 314 can be generally manufactured of cobalt-chromium-molybdenum alloy or other suitable biocompatible materials.

Attaching the mobile bearing component 316 to the medial portion 320 of the tibial tray 314 will now be described according to one example. At the outset, the surgeon can select a given medial bearing component 316 from a plurality of medial bearing components (see also kit 600, FIG. 21) that satisfies the desired characteristics for a given patient, such as height, articulation, etc. The mobile bearing portion 332 can be initially advanced into the pocket 334 superiorly, such that the tabs 352 can generally locate against the rail 346 formed on the fixed portion 330. Concurrently or subsequently, the fixed portion 330 can be located onto the medial portion 320 of the tibial tray 314 along with the mobile bearing portion 332 in an assembly. Next, a surgeon can slidably advance the mobile bearing component 316 in a directly generally posteriorly such that the channel 342 is progressively advanced around the locating tab 370 and the groove 348 of the fixed portion 330 is located under the lip 376 of the retaining rail 375 on the tibial tray 314. It will be appreciated that at this point, the fixed portion 330 remains static relative to the medial portion 320 of the tibial tray 314 while the mobile bearing portion 332 is free to slidably advance around the medial portion 320 of the tibial tray 314 within the confines of the surrounding wall 336 of the pocket 334. It can be appreciated that articulation of the medial condyle portion 20 of the femoral component on the superior articulating surface 358 of the mobile bearing portion 332 can influence the mobile bearing portion 332 to rotate and/or slidably advance such as in an anterior/posterior direction along the medial portion 320 around the pocket 334.

Connection of the fixed bearing component 318 to the lateral portion 322 of the tibial tray 314 is similarly carried out. Initially, the inferior surface 364 of the fixed bearing component 318 is located onto the lateral portion 322 of the tibial tray 314. Next, the fixed bearing component 318 is slidably advanced posteriorly, such that the channel 362 slidably accommodates the locating tab 372 while the groove 368 locates under the lip 380. The fixed bearing component 318 is adapted to be statically secured relative to the lateral portion 322 of the tibial tray when assembled.

With reference now to FIGS. 17-19, a tibial tray assembly 413 constructed in accordance to additional features of the present teachings will be described. As with the other knee prosthesis assemblies disclosed herein, the tibial tray assembly 413 can be patient specific, such that each component can be constructed for optimal features for a given patient. In this regard, the tibial tray assembly 413 can include a tibial tray 414, a first bearing component 416, a second bearing component 418 and a locking bar 420. As with the tibial tray 314 described above, the tibial tray 414 can be generally U-shaped and provides a slot 422 that can be configured to accommodate and provide clearance for a host ACL and/or PCL or a reconstructed ACL and/or PCL. Other examples of attaching an artificial or natural ACL and/or PCL may be found in “Knee Prosthesis Assembly with Ligament Link” Ser. Nos. 12/788,966 and 12/788,973, filed concurrently herewith. As with the other bearing components disclosed herein, the first bearing component 416 and the second bearing component 418 are both independently formed and intraoperatively selected according to the needs of a given patient. The first bearing component 416 and the second bearing component 418 are generally fixed bearing components, however, a mobile bearing component may be similarly provided for either of the medial and/or lateral sides. As will become appreciated from the following discussion, the locking bar 420 can be used to selectively and intraoperatively secure the respective first and second bearing components 416 and 418 to the tibial tray 414. The first bearing component 416 can have a superior surface 424, an inferior surface 426 (FIG. 19) having engagement grooves 427 and an anterior channel 428. Similarly, the second bearing component 418 can include a superior surface 430, an inferior surface 432 (FIG. 19) having engagement grooves 433 and an anterior channel 434.

The tibial tray 414 can include a medial portion 436, a lateral portion 438, posterior engagement tabs 440, an anterior engagement bridge 442 and anterior engagement tabs 443. The anterior engagement bridge 442 can include a track 444 formed thereon. The anterior engagement bridge 442 can provide an increased thickness to the tibial tray 414 at the connection between the medial and lateral portion 436 and 438, respectively to increase durability. A wall 446 can be formed on the anterior engagement bridge 442 adjacent to the track 444. The tibial tray 414 can have inferiorly extending posts 450.

The locking bar 420 can generally include a body 454 having a finger 456 extending therefrom. A catch 458 can be formed on a terminal end of the finger 456. The locking bar 420 can be formed of biocompatible metallic material, such as titanium for example. The body 454 can further include a leading end 460 and a trailing end 462.

Attaching the respective first and second bearing components 416 and 418 to the tibial tray 414 according to one example of the present teachings will now be described. Once a surgeon has selected a first and second bearing component 416 and 418 that satisfies the given needs of a particular patient (see also kit 600, FIG. 21), they are independently located onto the medial and lateral portions 436 and 438 of the tibial tray 414. In this regard, the posterior engagement tabs 440 of the tibial tray 414 can locate into the respective engagement grooves 427 and 433 of the first and second bearing components 416 and 418. In some examples, the respective first and second bearing components 416 and 418 may be advanced posteriorly, such that the engagement tabs 440 can lock into the engagement grooves 427 and 433. Concurrently, the anterior tabs 443 can locate into the anterior engagement grooves 427 and 433 of the first and second bearing components 416 and 418. Next, a surgeon can slidably advance the leading end 460 of the locking bar 420 through the respective anterior channels 428 and 434 of the first and second bearing components 416 and 418. Concurrently, a portion of the body 454 can locate along a posterior side of the anterior engagement bridge 442 while the finger 456 locates around an anterior side of the anterior engagement bridge 442. The locking bar 420 can be further advanced until the catch 458 on the finger 456 can locate around the wall 446 on the anterior engagement bridge 442.

With reference now to FIG. 20, another tibial tray 514 constructed in accordance to the present teachings is shown. The tibial tray 514 generally includes an inferiorly extending stem 516. The tibial tray 514 can be a full tibial tray that can be particularly suited for examples where a central slot (such as the slot 422) for accommodating an ACL is not needed. The tibial tray 514 includes posterior engagement tabs 540 and an anterior engagement bridge 542. Anterior locating tabs 543 can be formed on the tray 514. The anterior engagement bridge 542 can include a track 544. The tibial tray 514 can be configured to selectively and intraoperatively secure independent medial and lateral bearings, such as the bearings 416 and 418 disclosed herein.

Turning now to FIG. 21, a kit 600 is shown having a collection of medial and lateral bearings that provide unique articulations, sizes and thicknesses (i.e., D1, D2, D3, etc.) and incorporate either a fixed or mobile configuration on the lateral and medial sides. The kit 600 further includes the bicruciate retaining tibial tray and the posterior cruciate retaining tray. As disclosed herein, the kit can be particularly suited for allowing a surgeon the opportunity to intraoperatively select a given medial and/or lateral bearing component and tibial tray that is particularly suited for a given patient. It is contemplated that with the kit 600, a surgeon can also utilize the components during a revision surgery where the level of constraint needs to be increased. In this regard, a surgeon may only desire to change some components while leaving others unchanged.

As used herein, the terms superior, superiorly, superior direction are used to generally refer to the anatomical meaning, such as higher in place or position or generally situated above. Similarly, the terms inferior, inferiorly, inferior direction are used to generally refer to the anatomical meaning, such as lower in place or position or generally situated below.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 

What is claimed is:
 1. A knee joint prosthesis assembly comprising: a femoral component having a medial and a lateral condyle portion connected by a patellar track portion, the femoral component forming an opening between the medial and lateral condyles; a unitary tibial component having a medial portion that includes a first engagement structure and a lateral portion that includes a second engagement structure; a medial bearing having a third engagement structure formed thereon that selectively engages the first engagement structure; and a lateral bearing separately formed and independent from the medial bearing and having a fourth engagement structure formed thereon that selectively engages the second engagement structure; wherein one of the medial and lateral bearings is fixed relative to the tibial component and the other of the medial and lateral bearings is a mobile bearing component; wherein the mobile bearing component includes: a fixed portion having a superior surface configured to cooperate with one of the medial or lateral condyle portions of the femoral component, and having the third engagement structure or the fourth engagement structure that is configured to statically engage the tibial component; and a mobile bearing portion having a superior articulating surface configured to cooperate with said medial or lateral condyle portions of the femoral component, said mobile bearing portion being configured to slidably advance along a superior surface of the tibial component.
 2. The knee joint prosthesis of claim 1 wherein the fixed portion defines a pocket that receives and confines the mobile bearing portion therewithin.
 3. The knee joint prosthesis of claim 2 wherein the mobile bearing portion is formed of a polymeric material and includes a metallic layer of material disposed around a perimeter thereof.
 4. The knee joint prosthesis of claim 3 wherein the mobile bearing portion comprises a pair of tabs extending therefrom that communicate with the fixed portion during movement of the mobile bearing portion.
 5. The knee joint prosthesis of claim 4 wherein the fixed portion defines a pair of complementary channels formed thereon that guide the tabs of the mobile bearing portion.
 6. The knee joint prosthesis of claim 4 wherein the tabs extend from opposite sides of the mobile bearing portion.
 7. The knee joint prosthesis assembly of claim 2, wherein the mobile bearing portion includes an outer perimeter surface extending from a superior articulating surface thereof, a surrounding wall of the pocket surrounds the outer perimeter surface of the mobile bearing portion.
 8. The knee joint prosthesis of claim 1 wherein the mobile bearing portion is formed of polyetheretherkatone (PEEK).
 9. The knee joint prosthesis of claim 1 wherein the mobile bearing portion is formed of polyethylene.
 10. A knee joint prosthesis assembly comprising: a femoral component having a medial and a lateral condyle portion connected by a patellar track portion, the femoral component forming an opening between the medial and lateral condyles; a unitary tibial component having a medial portion that includes a first engagement structure and a lateral portion that includes a second engagement structure; a medial bearing having a third engagement structure formed thereon that selectively engages the first engagement structure; and a lateral bearing separately formed and independent from the medial bearing and having a fourth engagement structure formed thereon that selectively engages the second engagement structure; wherein one of the medial and lateral bearings is a mobile bearing component having a fixed bearing portion that defines a closed pocket, and a mobile bearing portion disposed and confined for movement within the closed pocket such that the mobile bearing portion is surrounded by the closed pocket, wherein the fixed bearing portion has a superior surface configured to cooperate with one of the medial or lateral condyle portions of the femoral component; and wherein the mobile bearing portion having a superior articulating surface configured to cooperate with said medial or lateral condyle portions of the femoral component, said mobile bearing portion being configured to slidably advance along a superior surface of the tibial component.
 11. The knee joint prosthesis of claim 10 wherein the mobile bearing portion is formed of a polymeric material and includes a metallic layer of material disposed around a perimeter thereof.
 12. The knee joint prosthesis of claim 10 wherein the mobile bearing portion comprises a pair of tabs extending therefrom that communicate with the fixed portion during movement of the mobile bearing portion.
 13. The knee joint prosthesis of claim 12 wherein the fixed portion defines a pair of complementary channels formed thereon that guide the tabs of the mobile bearing portion.
 14. The knee joint prosthesis of claim 12 wherein the tabs extend from opposite sides of the mobile bearing portion.
 15. The knee joint prosthesis of claim 10 wherein the mobile bearing portion is formed of polyetheretherkatone (PEEK).
 16. The knee joint prosthesis of claim 10 wherein the mobile bearing portion is formed of polyethylene.
 17. The knee joint prosthesis of claim 10 wherein the tibial component is U-shaped and is adapted to accommodate an anterior cruciate ligament.
 18. The knee joint prosthesis assembly of claim 10, wherein the closed pocket extends through the fixed bearing from a superior end to an inferior end thereof to permit an inferior surface of the mobile bearing portion to abut the unitary tibial component. 